The invention generally relates to an adjusting apparatus for a thermal release of a switching device. A switching device is understood here to be a mechanical or electromechanical switching device, in particular power breakers, circuit breakers, relays, contactors and the like.
An adjusting apparatus is known from EP 0 913 848 A2.
A switching device serves the purpose of connecting a circuit to an electrical power supply system and isolating the circuit manually and automatically from the supply system if the current exceeds a predetermined value. A power breaker, for example, thus serves the purpose of protecting lines in installations and systems from overload and short circuit In a supply system having a shutdown facility using overcurrent protection devices for disconnection, such a switching device also prevents touch voltages which are too high from being maintained in the event of a fault.
When the switching device or circuit breaker is switched on, an energy store, for example a spring, is stressed as part of a mechanical switching mechanism or breaker mechanism, is released for the tripping operation and operates the switch. Here, the switching device includes a thermal release in the form of a bimetallic element which is usually in the form of a strip and which trips with a delay depending on the overload duration. The tripping operation is initiated by thermal deformation of the bimetallic strip as a result of the overcurrent passing through it. For this purpose, the bimetallic strip acts on a tripping lever which is opposite the free end of the bimetallic strip, spaced apart from it, and is mechanically coupled to the breaker mechanism. The tripping lever thus causes the bimetallic strip to release the breaker mechanism whilst the energy store of the breaker mechanism opens a moveable contact or moving contact by lifting the contact from a fixed contact. In addition, the switching device also usually includes a magnetic or electromagnetic release, which trips without a delay, for high surge and short-circuit currents.
The distance between the free end of the bimetallic element and the tripping lever is to be designed to be adjustable, for which purpose an adjusting screw is usually provided. Switching devices in which such an adjusting screw is used to adjust the bimetallic element are known, for example, from DE 1 904 731 A1 and from EP 0 143 981 A1 as well as from EP 0 412 953 A3. The use of an adjusting screw does, however, entail corresponding production and manufacturing costs.
EP 0 913 848 A2 also discloses a method for thermally calibrating the tripping mechanism of a switching device and a corresponding tripping mechanism, in which the adjustment is carried out thermally, by way of a laser.
An embodiment of the invention is based on an object of proposing a particularly cost-effective adjusting apparatus, which is easy to operate, for a switching device, in particular for a power breaker.
For this purpose, the distance between the tripping lever and the free end, which acts on the tripping lever increasingly as a result of thermal deformation in the tripping direction, of the bimetallic element can be set by bending a bimetallic support which is firmly connected to the bimetallic element.
Here, the bimetallic support has at least one predetermined bending point, preferably two or three predetermined bending points. By this, the bimetallic support acts as a multi-link chain or multi-joint mechanism when it is fixed or mounted in the enclosure of such a switching device. The bimetallic support has, in the region of a first predetermined bending point, a retaining limb, which runs parallel to the bimetallic element and is connected to its contact end, as well as an operating limb, which runs at least approximately transversely with respect to the retaining limb. The free end of the operating limb can be guided in or against an enclosure profile, this free end being guided or held, by way of a corresponding actuating tool, such that it can pivot on a bending path which is at least approximately in the form of a circular arc.
A further, second predetermined bending point may be provided either along the retaining limb or on the limb end of the retaining limb which is remote from the operating limb. In this embodiment, the bimetallic support merges at this second predetermined bending point with a fixing limb which runs transversely with respect to the retaining limb, expediently at an obtuse angle. The fixing limb itself is then expediently in turn bent back twice, resulting in an overall approximately U-shaped fixing limb and thus a bimetallic support which is bent, overall, in the form of a ring or a loop.
With this configuration, which is, for example, in the form of a ring or a loop, of the bimetallic support, the operating limb which extends from the first predetermined bending point is bent inward or outward. If the operating limb is bent outward, its end is guided against an adjustment profile in the form of an arc. This profile is preferably provided by an appropriate enclosure profile of the switching device.
This adjustment or enclosure profile which is in the form of an arc has a diminishing radius in which the operating limb lies. When the operating limb is rotated about the first predetermined bending point, forming a pivot, against the adjustment profile, the bimetallic support is bent and thus the position of the bimetallic element is changed for the purpose of adjusting the bimetallic element. Here, the transformation ratio of the angle of rotation of the operating limb to the movement of the free end of the bimetallic element can be set, depending on the requirements, by correspondingly configuring the adjustment and enclosure profile.
When the operating limb is bent inward, a further (third) predetermined bending point is expediently provided along the operating limb. A positioning pin, which runs transversely with respect to the longitudinal direction of the limb and can be fixed in position in a positioning opening, which is in a fixed position, in the enclosure of the switching device, is then integrally formed on the operating limb between this (third) predetermined bending point and the free end of the operating limb.
In this embodiment of the bimetallic support and thus of the adjusting apparatus, too, the bimetallic support is in turn bent by rotating the operating limb about the pivots formed by the two predetermined bending points, and thus the position of the bimetallic element is changed for adjustment purposes. In both embodiments, the distance between the free end of the bimetallic element or the tip of the bimetallic element and the tripping lever is thus set or adjusted by bending the bimetallic support. The predetermined bending points are expediently formed by material cutouts in the corresponding vertices of the bends in the bimetallic support.
Advantages achieved by an embodiment of the invention include, in particular, the fact that, by appropriately configuring and arranging a bimetallic support bearing the bimetallic element, it is possible to bend the the bimetallic support specifically and thus to provide a simple and cost-effective adjusting apparatus for a thermal release of a switching device.
This mechanism, which serves the purpose of adjusting the bimetallic element and in which the bimetallic support, which is expediently provided with predetermined bending points, acts in the manner of a multi-link chain, in particular a three- or four-link chain, also makes possible virtually automatic or independent compensation for subsequent shrinkage of the enclosure. Such shrinkage, to which enclosure materials which are usually used are subject, leads, over the life of the device, to undesirable changes in important structural and dimensional proportions, such as, in particular, the distance between the tip of the bimetallic element and the tripping lever, and thus to an undesirable maladjustment or displacement of the thermal release as well.